Science Applications International Corporation

Science Applications Incorporated Corporation

David A Eitman

William A Clarke

Kenneth M Kratsch

Oxidation resistant coatings on carbon fibers are provided. Oxidation inhibitor particles are incorporated into a polymeric sizing coating on carbon fibers to protect the fibers from deterioration and erosion due to oxidation of carbon.

Method of applying oxidation resistant coating on carbon fibers

A porous substrate is formed from an agglomeration of fibers preferably has a carbonaceous composition and a binder is applied to the substrate. The binder may illustratively be an acrylic or beeswax to vaporize during pyrolysis or may illustratively be a phenolic resin, a furfural resin or pitch to retain pyrolyzed carbon on the fibers after pyrolysis. A mixture of particles having the same approximate size as the diameter of the fibers is then applied to the fibers to become mechanically locked in the substrate pores. The mixture may contain (a) a first material (preferably a compound containing boron) which oxidizes and melts at a relatively low temperature and is relatively viscous when melted, (b) a second material (preferably a compound containing silicon) which oxidizes and has an increased melting temperature and is more viscous than the first material when melted and (c) a refractory material (preferably a compound containing zirconium) having a considerably higher melting temperature oxide than the first and second materials. The first material may be obtained from group 3a of the periodic table, the second material from group 4a of the periodic table and the third material from groups 4b and 5b of the periodic table. An impermeable coating such as a carbide, oxide or a nitride is thereafter applied to the substrate. The impermeable coating tends to crack at elevated temperatures. The adjacent particles in the mixture melt and flow into the cracks to inhibit crack amplification, the ease of flow is dependent upon the proportions of the first, second and third materials on the mixture. The particles displaced in the mixture from the cracks remain mechanically looked to the substrate.

Refractory composite articles and method of making such articles

A porous substrate formed from an agglomeration of fibers preferably has a carbonaceous composition. A binder is applied to the substrate. The binder may illustratively be an acrylic or beeswax to vaporize and form pyrolized carbon during pyrolysis or may illustratively be a phenolic resin, a furfural resin or pitch to form pyrolyzed carbon on the fibers during pyrolysis. A mixture of particles having the same approximate size as the diameter of the fibers is then applied to the fibers to become mechanically locked in the substrate pores. The mixture may contain (a) a first material (preferably a compound containing boron) which oxidizes and melts at a relatively low temperature and is relatively viscous when melted, (b) a second material (preferably a compound containing silicon) which oxidizes and has an increased melting temperature and is more viscous than the first material when melted and (c) a refractory material (preferably a compound containing zirconium) having a considerably higher melting temperature oxide than the first and second materials. The first material may be obtained from group 3a of the periodic table, the second material from group 4a of the periodic table and the third material from groups 4b and 5b of the periodic table. An impermeable coating such as a carbide, oxide or a nitride is thereafter applied to the substrate. The impermeable coating tends to crack at elevated temperatures. The adjacent particles in the mixture melt and flow into the cracks to inhibit crack amplification. The ease of flow is dependent upon the proportions of the first, second and third materials in the mixture. The particles displaced in the mixture from the cracks remain mechanically locked to the substrate.

Refractory composite articles

An improved method for the fabrication of a reinforced composite. The method includes assembling rigid rods into a geometric structure such that all interstitial voids are interconnected, infiltrating the geometric structure with particles, impregnating the infiltrated geometric structure with an appropriate liquid matrix binder or precursor, and treating the impregnated geometric structure such that the binder solidifies to form the reinforced composite.

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Huntington Beach, CA, United States of America

David A Eitman